1. Field of the Invention
The present invention relates to a novel process for the preparation of aromatic diamines containing a diorganopolysiloxane linkage, and, more especially, to a novel process for the preparation of alpha, omega-bis(aminophenoxyalkyl)diorganopolysiloxanes.
2. Description of the Prior Art
The subject diamines are compounds which are known to this art. They are described, for example, in British Pat. No. 1,062,418 and U.S. Pat. No. 4,395,527; they may be represented by the following general formula: ##STR2## in which:
X, which is in the ortho, meta or para position relative to the carbon atom of the benzene ring bonded to nitrogen, represents, for example, an atom or group below: ##STR3##
R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5, which may be identical or different, each represent, for example, a monovalent hydrocarbon radical selected from among straight or branched chain alkyl radicals containing from 1 to 12 carbon atoms, or substituted such radicals bearing one or more chlorine, bromine or fluorine atom substituents or a --CN group; and a phenyl radical optionally substituted by one or more alkyl and/or alkoxy radicals containing from 1 to 4 carbon atoms or by one or more chlorine atoms;
the symbol x is an integer within the range, for example, of from 2 to 8; and
the symbols y and z represent integers or real numbers, which may be identical or different, the sum of which is, for example, within the range from 0 to 100.
For a compound of this type, when y and/or z are greater than 1, this is a compound having a polymeric structure and is rarely a single compound, but most frequently a mixture of compounds of the same chemical structure, which differ by the number of recurring units in their molecule. This provides an average value for y and/or z which may be an integer or a real number.
The practical value of these diamines containing a diorganopolysiloxane linkage is in their use as additives in lubricant compositions or surface-coating compositions, or in yet other applications, for example, as intermediates for the preparation of copolymers.
In accordance with the patents noted above, a first method for the preparation of these diamines, especially applicable when it is sought to prepare a compound in which y=z=0, i.e., when a diamine containing a diorganodisiloxane group is produced, consists in reacting a compound of the formula: ##STR4## in which X is as defined above and M is an alkali metal or an alkaline earth metal, with a bis(haloalkyl)disiloxane of the formula: ##STR5## in which x has the value given above and Y is a chlorine, bromine or iodine atom, and conducting the reaction at a temperature of from 20.degree. to 200.degree. C. in the presence of an aprotic polar solvent.
In the case where it is desired to prepare a diamine in which y and/or z are other than O, a second preparation technique is described which consists in copolymerizing one mole of the diamine containing a diorganodisiloxane linkage prepared as mentioned above, with a quantity of one or more cyclic diorganopolysiloxanes adapted to provide y moles of siloxy group of the formula: ##STR6## and/or z moles of siloxy groups of the formula: ##STR7##
The reaction is generally carried out at a temperature of from 80.degree. to 250.degree. C. in the presence, in this case as well, of a solvent and, optionally, in the presence of a suitable catalyst.
However, these prior art processes present a number of disadvantages such that their industrial value is minimized. In particular, it is observed that the majority of syntheses are carried out in solution in an organic solvent medium, which generally requires, upon completion of the reaction, one or more additional stages of distillation under reduced pressure in order to remove the reaction solvent. Additional equipment suitable for recovering the removed solvent and for purifying same prior to its recycle is also required. Moreover, on detailed examination of the prior art processes, for example those described in the aforenoted patents for the preparation of alpha, omega-bis(aminophenoxyalkyl)polysiloxanes, it is observed that the temperatures and the reaction times employed in practice are generally fairly high: on the one hand, 7 to 8 hours of reaction between 110.degree. and 122.degree. are required in order to prepare the starting reagent of the formula: ##STR8## and, one the other hand, about an additional 16 hours of reaction are required after the addition of the bis(haloalkyl)disiloxane into the reaction medium. Finally, it appears from the prior art patents that the yields of the diamine desired do not exceed 85%